• 소성∙가공
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• 제19권8호
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• pp.480-485
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• 2010

In this work, the closing behavior of cylindrical-shaped voids was experimentally investigated according to various parameters such as reduction ratio in height, initial void size and billet rotation during hot open die forging process. The reduction ratio in height, number of path, and billet rotation were chosen as key process parameters which influence the void closing behavior including the change of void shape and size. On the other hand, values of die overlapping and die width ratio were set to be constant. Void closing behavior was estimated by microscopic observation. Based on the observations, it was confirmed that application of billet rotation is more efficient to eliminate the void with less reduction ratio in height. The experimental results obtained from this study could be helpful to establish the optimum path schedule of open die forging process.

• Journal of Magnetics
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• 제11권3호
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• pp.103-107
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• 2006

In grain oriented electrical steel process, hot band annealing has thought to be essential for obtaining good magnetic properties. New hot rolling method of heavy reduction in early hot rolling stage was applied to obtain good magnetic properties in GO process without hot band annealing. Hot rolling was carried out by varyinghot rolling reduction distribution along hot rolling pass. The heavy hot rolling reduction in rear stand improves the magnetic flux density in the case of no hot band annealing. The hot band specimens of the heavy reduction in front stand shows the elongated hot deformed microstructures in the center layer and strong {001}<110> texture.On the contrary, the heavily reduced specimens in rear stand shows the recrystallization in the center layer of hot band and strong {111}<112> and {110}<001> textures.

• Journal of Electrochemical Science and Technology
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• 제5권3호
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• pp.65-72
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• 2014

The use of nanoscale electrocatalysts is a promising strategy for achieving high catalyst activity due to their large surface area. However, catalyst activity is not directly correlated to particle size. To understand this discrepancy, many studies have been conducted, but a full understanding has still not been achieved, despite the importance of particle size effects in designing an active catalyst. In this review, we focus on the discussion of particle size effects on the oxygen reduction reaction, and also discussed the nanoscale design beyond the nanoparticle to the meso and macroscale design.

• 한국분말재료학회지
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• 제22권4호
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• pp.260-265
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• 2015

Spherical fine cobalt powders were fabricated by new liquid reduction method. Commercial cobalt sufate heptahydrate was used as raw material. Also ethylene glycol was used as solvent and hydrazine-sodium hypophosphite mixture was used as reduction agent for the new liquid reduction method. A plate shaped cobalt powders with an approximately 300 nm were prepared by a traditional wet ruduction method using distilled water as solvent and hydrazine. Spherical fine cobalt powders with an average size of $1-3{\mu}m$ were synthesized by a new liquid reduction method in 0.3M cobalt sulfate and 1.5M hydrazine-0.6M sodium hypophosphite mixture at 333K.

• 한국세라믹학회지
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• 제30권4호
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• pp.279-288
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• 1993

A study on calcination and reduction of AUC(ammonium uranyl carbonate, (NH4)4UO2(CO3)3) has been carried out by using TG-DTA in N2, air and H2 atmospheres, respectively. Phases of various intermediate obtained during thermal analysis of AUC in different atmospheres were confirmed by XRD. Powder characteristics of each intermediate were investigated by measuring particle size and specific surface area, and also observed by SEM. As a results, regardless of applied atmosphere AUC was calcined into amorphous UO3, which was converted to $\alpha$-U3O8 Via $\alpha$-UO3 in both H2 and N2 atmosphere, but directly into $\alpha$-UO3 in air atmosphere. Further reduction of U3O8 was only detectable in hydrogen atmosphere. During calcination and reduction, average particle size was reduced to less than 30% of original value without morphology change. Specific surface area was dramatically increased with release of NH3, CO2 and H2O from AUC powder and reached maximum value around 25$0^{\circ}C$, and then gradually decreased with the increase of temperature due to sintering effect of uranium oxides such as UO3 and U3O8. It was also found that the change of average crystallite size and pore size were closely related to the changes of specific surface area of uranium oxides.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1420-1423
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• 2005

Micro Cellular Plastics create a sensation at polymer industrial for lowering product cost & overcoming a lowering of mechanical intensity. Reduction of MCPs cell size increases the intensity of MCPs. This research based on the experiment about cell size reduction method. At this study, Quenching & Pressure foaming process are introduced to one of methods. Conclusion of study is that Quenching process is the simplest process for nano cell formation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권6호
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• pp.2554-2580
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• 2018

Lenstra-Lenstra-$Lov{\acute{a}}sz$ (LLL) is an effective receiving algorithm for Multiple-Input-Multiple-Output (MIMO) systems, which is believed can achieve full diversity in MIMO detection of fading channels. However, the LLL algorithm features polynomial complexity and shows poor performance in terms of convergence. The reduction of algorithmic complexity and the acceleration of convergence are key problems in optimizing the LLL algorithm. In this paper, a variant of the LLL algorithm, the Hybrid-Fix-and-Round LLL algorithm, which combines both fix and round measurements in the size reduction procedure, is proposed. By utilizing fix operation, the algorithmic procedure is altered and the size reduction procedure is skipped by the hybrid algorithm with significantly higher probability. As a consequence, the simulation results reveal that the Hybrid-Fix-and-Round-LLL algorithm carries a faster rate of convergence compared to the original LLL algorithm, and its algorithmic complexity is at most one order lower than original LLL algorithm in real field. Comparing to other families of LLL algorithm, Hybrid-Fix-and-Round-LLL algorithm can make a better compromise in performance and algorithmic complexity.

• 전기학회논문지
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• 제66권6호
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• pp.981-987
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• 2017

In this paper, we describe the LPM structure with a two-phase, which is not used previously, and explain its operation principle. In order to predict the accurate performance of LPM reduction model, finite element model was derived and the back EMF of LPM reduction model was measured and compared. In order to investigate the thrust and normal force of the LPM reduction model, a driving circuit capable of applying two-phase pulse currents was constructed and the performance was predicted in conjunction with the finite element analysis model. Finally, the design considering actual LPM size was performed. Since the size of the reduction model is small, the field could be made of a permanent magnet. However, it is almost impossible to manufacture a permanent magnet to match the size and capacity of a real LPM for a vehicle, in terms of cost and writing. Therefore, the actual vehicle LPM was replaced by wound type that generates a magnetic field by applying current to the field winding, and the final model was derived using the reaction surface method.

• 한국생활과학회지
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• 제15권5호
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• pp.791-802
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• 2006

The construction of athlete's tight-fitting garments by reducing the elastic knit pattern is an interesting subject, which directly influences the performance of the wearer. Therefore, relationships between the reduction rates of the men's pants pattern obtained using measurements of Size Korea 2004 and clothing fitting were explored to improve clothing comfort. Two pattern making methods were developed and the reduction rates were applied to those pants depending on the parts of human body. The four male subjects were university students in the ages of 20 to 24. Subjective wear sensations of the experimental garments were rated using seven Likert scales during 4 consecutive days. While wearing the garments, subjects were kept four various postures including waist flexion and sitting etc by requests of the researchers. Likert type scale was used for the evaluation and 7 point indicates that it gave the best fit as tight-fitting pants. As results, differences in the length and girth between two piece pants pattern(style 1) and one piece pants pattern(style 2) were 0.0$\sim$0.3cm. Between two pattern making methods, one piece pants pattern(the style 2) was superior to two piece pants pattern in terms of subjective sensation and fit. Among eight tight-fitting pants, C, D, G, H pants were superior in terms of fitting and stability of waist and hip part to the others. ill case of tight-fitting pants, the reduction rate of the pattern in the course direction, the reduction rate of T2/3(66%) was better than that of T/2(50%), but the reduction rate of the pattern in the wale direction, that of the part of crotch, which was very sensitive part, should be kept the same as suggested earlier by Ziegert(1988).

• 자원리싸이클링
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• 제14권1호
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• pp.26-32
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• 2005

국내 폐은 원료로부터 고부가가치 Ag powder를 제조하기 위한 연구의 일환으로써 ascorbic acid를 환원제로 사용한 Ag 미립자 제조실험을 수행하였다. Ag 수용액은 질산은을 10~120 mmole/l의 범위로 용해시켜 사용하였으며, Ag 미립자의 응집방지를 위한 분산제로는 Tamol NN8906 및 PVP를 각각 사용하였다. 환원반응을 통하여 제조한 Ag 미립자는 X-선 회절분석, 입도분석, SEM 및 TEM 분석을 실시하여 morphology 와 평균입도를 측정하였다. ascorbic acid에 의한 수용액중 Ag 이온의 환원반응은 10분 이내에 거의 평형상태에 도달하였으며, 완전한 Ag 이온의 환원을 위해서는 ascorbic acid 첨가량이 이론치의 1.6배가 소요되었다. 생성된 Ag 미립자의 입도분포는 bimodal 혹은 trimodal의 분포곡선을 보였으며, Ag 미립자의 평균입도는 분산제 종류 및 첨가량과 수용액 중 초기 Ag 농도에 따라 달라지는 것으로 나타났다.